i have to go fight, and i took off for a year to go fight in afghanistan. >> reporter: he spent 2002 and 2003 near kandahar hunting for taliban. he came back in harvard, but in 2009 with the national guard unit he went back to afghanistan. >> i spent a lot of time with rock clearance units, looking for ieds, and my vehicle never got hit and i am very lucky, very lucky. when you go up and pull open the door and see your injured buddies, you never forget that sight. >> reporter: he began to explore the science of brain injury. when the brain gets hit by a blast wave, it slams up against the skull. >> reporter: he developed new tools to study how the blast hurts the brain. >> concussions that your favorite football player suffers, or the head injury you get in a car accident or shaken baby syndrome, those are all examples of head injuries that can cause a traumatic head injury. >> more than half a dozen students are veterans. >> we're focused on this, because these are our buddies, our guys, and this could have been us, and it might still be us. so it brings a certain level of urgency t